add dot before first integer in all lines - regex

Question

I have lines like
Input:
abcd1234
bdfghks4506
agfdch6985
I would like to add "." before the first integer in line, how do I do it?
Output:
abcd.1234
bdfghks.4506
agfdch.6985

Answer 1

This might work for you (GNU sed):
sed -i 's/[[:digit:]]/.&/' file
If there is a digit in a line, put a . before it.
N.B. To put a . before every digit in a file use:
sed -i 's/[[:digit:]]/.&/g' file

Answer 2

$ cat > input.txt
abcd1234
bdfghks4506
agfdch6985
$ sed -e 's/^\([^0-9]*\)\([0-9]\)\(.*\)$/\1.\2\3/' input.txt
abcd.1234
bdfghks.4506
agfdch.6985
Use sed string replacement with regular expression capture groups.
Match the beginning of the line.
Start a capture group that matches any number of non-numeric characters.
Start a second capture group that matches a single digit.
Start a third capture group that matches the remainder of the line.
Match the end of the line.
Replace the entire line with the contents of the first capture group, ".", the second capture group and, finally, the third capture group.

Answer 3

The function sub of awk may help,
$ awk 'sub(/[0-9]/,".&",$0)1' file
abcd.1234
bdfghks.4506
agfdch.6985
Brief explanation,
sub: replace only the first matching substring in each line
&: is replaced with the text that was actually matched (i.e. [0-9])
Appended 1: to print the result.

Answer 4

The most strict command for your case would be
sed -E -i 's/([a-z])([1-9])/\1\.\2/' file.txt
-E Use extended regex
-i '' Replace in file (instead of writing to output)
This will match any example you provided

Answer 5

Not familiar with awk / sed specifically, but a regex replace using this regex should be all you need:
Search: (\d+.*?)$ (match everything from the first found number to the end of the line)
Replace by: .$1 (captured group #1 prefixed by a literal .)
The notation of the capture group in the replace command may differ depending on the implementation. I used $1 here, but some implementations may use \1.